Flow dynamics and tributary mouth bar formation at river confluences with high rates of tributary sediment supply
Bibliographic record
Abstract
River confluences influence the formation of secondary circulation, bed morphology, and associated feedbacks. With distance downstream through a drainage network, it becomes likely that the flow momentum of tributaries is lower than that of the main river, creating confluences with very low momentum ratio. However, the tributary may be able to supply significant quantities of sediment, especially in watersheds with high relief. High flow and sediment supply events in the tributary may decouple in time from those in the main river. The capacity of the main river to evacuate tributary-delivered sediment may occasionally be lower than the sediment delivery rate. The result is the formation of confluences with large tributary mouth bars that may influence confluence flow structures even when the tributary discharge has declined. There are no field examples measured to date for such confluences. Here, we report the first field data for three such river confluences, along the upper Rhône River, Switzerland. We combine aDcp measurements with the analysis of the provenance of sediments in the tributaries and main stem. We introduce the angular momentum ratio for confluence classification. The formation of tributary mouth bars and a scour hole was identified for the two junctions with significant tributary sediment supply. These bars were sufficient to introduce secondary circulation even at very low flow momentum ratios. The analysis of sediment provenance suggested that the origin of the bars was not necessarily the tributary but could be a consequence of the effects of the tributary upon main channel sediment routing.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".